ALICE-LHCC Review January 29-30, 2001 Thomas C. Meyer/EP-AIT1 General Layout Four separate vessels: –Outer containment vessel –Inner containment vessel –Outer field cage vessel –Inner field cage vessel Two end plates for readout

ALICE-LHCC Review January 29-30, 2001 Thomas C. Meyer/EP-AIT2 Design Objectives Provide high stability and uniformity for: Gas gain (>10 4 ):0.5% Drift field (400 V/cm):E r /E z < Temperature:  T < 0.1 ºC Drift gas purity:5 ppm O 2, 10 ppm H 2 O Provide high mechanical precision for: Central electrode:250 µm Readout plane:250 µm

ALICE-LHCC Review January 29-30, 2001 Thomas C. Meyer/EP-AIT3 Technical Progress The FC prototype has undergone intensive testing during the past two years: –Individual components (electrical, mechanical, gas) –System behavior (FC + NA35 readout chamber, cosmics & laser runs) Laboratory results certify the required performance of the FC in terms of field quality. High radiation test in CERES area: –Check stability under ‘realistic’ conditions –Exposed FC to proton and Pb beams

ALICE-LHCC Review January 29-30, 2001 Thomas C. Meyer/EP-AIT4 Test-Setup in CERES Zone

ALICE-LHCC Review January 29-30, 2001 Thomas C. Meyer/EP-AIT5 High Intensity: Proton Runs Direct exposure to proton beam: –Locally irradiated area (1-4 cm 2 ) near central electrode: Stable up to 100 kV CERES p-beam:2.5 x 10 5 /cm 2 s (3 x 10 5 with Pb target) ALICE:360/cm 2 s

ALICE-LHCC Review January 29-30, 2001 Thomas C. Meyer/EP-AIT6 High Intensity: Pb-Ion Runs Exposure to secondaries from Pb beam: –Global irradiation of entire cylinder Stable to ≤ 60 kV! CERES Pb-beam:6000/cm 2 s (secondaries) ALICE:360 /cm 2 s

ALICE-LHCC Review January 29-30, 2001 Thomas C. Meyer/EP-AIT7 Material Tests: Hygroscopy Check crucial material of field cage for hygroscopic behavior: –Kevlar (skins) –Carbon fiber (skins) –Glass fiber (skins) –Makrolon (rods) Pre-condition material Choose glass fiber instead of Kevlar Drying  L/L [µm/m] T [min] Macrolon Carbon Fiber Kevlar Fiber Glass Fiber Wet

ALICE-LHCC Review January 29-30, 2001 Thomas C. Meyer/EP-AIT8 Material Tests: Tedlar Does Tedlar provide an efficient moisture barrier? –Sandwich sample exposed to water-saturated air at 29 ºC on both sides: Maximum possible water absorption by matrix is 6% of sample weight, i.e g. After 18 days of exposure, no weight increase was observed. Reverse test is ongoing, i.e. the sandwich is placed in a 100% dry atmosphere.

ALICE-LHCC Review January 29-30, 2001 Thomas C. Meyer/EP-AIT9 Problems & Risks: Material Material tests basically finished. –Kevlar fallback: glass fiber (included in tender)  Slightly cheaper  More mass (<10% of total) –Tedlar fallback: none!  Aging tests planned (≥ 1 year) –Macrolon rods replaced by ceramics?  Very expensive (material and machining)

ALICE-LHCC Review January 29-30, 2001 Thomas C. Meyer/EP-AIT10 Cooling Tests: Resistor Chain Four internal resistor chains supply the appropriate potentials to the strips. Their power consumption is 60W each. This leads to temperature gradients inside TPC of »0.1 °C. Must cool the voltage divider!

ALICE-LHCC Review January 29-30, 2001 Thomas C. Meyer/EP-AIT11 Resistor Chain: Concept Voltage divider is placed inside rod. Liquid coolants to remove waste heat. First test with water successfully finished, as proof of principle.

ALICE-LHCC Review January 29-30, 2001 Thomas C. Meyer/EP-AIT12 Resistor Chain: Test-Setup The Thermal Box Resistor Rod

ALICE-LHCC Review January 29-30, 2001 Thomas C. Meyer/EP-AIT13 Resistor Chain: Results Achieve negligible temperature gradient inside rod: Pt 1Pt 2 Pt 3Pt 4Pt 5 H 2 O in H2OH2O

ALICE-LHCC Review January 29-30, 2001 Thomas C. Meyer/EP-AIT14 Resistor Cooling: Next Steps We have verified that water and silicon fluid FL 200/5 remove heat equivalent to 60 W, as expected. For HV operation, only non-polar liquids can be used: The liquid must be compatible with the rod material.

ALICE-LHCC Review January 29-30, 2001 Thomas C. Meyer/EP-AIT15 Problems & Risks: Charging Understand field cage charging under high radiation load: –Examine field cage in laboratory:  Bleed 300 MBe of 83 Kr into field cage gas to simulate charged particle flux.  Separate tests for drift and insulation volume. –Increase number of guard rings. –Eventually repeat beam test.

ALICE-LHCC Review January 29-30, 2001 Thomas C. Meyer/EP-AIT16 Problems & Risks: Cooling The resistor rod is a high risk item... –Choose liquid that is safe for apparatus.  No chemical decomposition, dissolution etc. –Run circuit below atmospheric pressure.  Absolutely no leaks, cracks, capillary effects! –Tight quality control. –If all fails, use gas as coolant:  Double walled cooling circuit;  Needs additional, extensive testing.

ALICE-LHCC Review January 29-30, 2001 Thomas C. Meyer/EP-AIT17 Stability Study: Why? Weights [N]: Rails ITS + Vac. Ch. Services ITS and beam pipe are supported by TPC. TPC moves (!) out for ITS interventions. Deformations must not harm TPC and ITS.

ALICE-LHCC Review January 29-30, 2001 Thomas C. Meyer/EP-AIT18 FEA: Critical Area Transition from solid Al flange to laminar composite structure 1.2 MPa 8.4 MPa 4.8 MPa 10.8 MPa Equivalent shear stress (van Mises) indicates critical zone

ALICE-LHCC Review January 29-30, 2001 Thomas C. Meyer/EP-AIT19 FEA: Results Buckling: –No buckling modes induced until load is increased by a factor of ~ 60. Stresses: –The critical zone is the transition from flange to cylinder (“ovalization” under load). –Maximum shear stress in glue joint is ≤ 3 MPa (factor of 6 from failure). –Interlaminar shear stress in composite matrix is ~ 5 kPa (6% risk of delamination)

ALICE-LHCC Review January 29-30, 2001 Thomas C. Meyer/EP-AIT20 Problems & Risks: Stability Flexible joint for central drum?: Removes load from critical zone Engineering design underway Lower cost than original version ITS attached here Critical zone

ALICE-LHCC Review January 29-30, 2001 Thomas C. Meyer/EP-AIT21 Problems Related to Contracting Cylinders: –Only five offers received –Lowest offer still 3 x higher than budget End Plates: –Lowest bid exceeds budget by factor of 5 –Splitting of production processes  Separate raw material, welding and machining –Design changes Alternative scenarios require new tenders –Could lead to delays and increased risks –Avoid market surveys (6 months delay)

ALICE-LHCC Review January 29-30, 2001 Thomas C. Meyer/EP-AIT22 Future Activities R&D and prototyping continues during construction in 2001: –Entire infrastructure of field cage  Central electrode (3 options)  Strips & Rods (4 different types)  Gas distribution  Alignment –Tooling and assembly techniques  Prepare DELPHI support frame  Test facilities (gas, survey, HV, LV, readout)

ALICE-LHCC Review January 29-30, 2001 Thomas C. Meyer/EP-AIT23 Project Schedule R & DDesign & PrototypingConstruction & AssemblyPhysics Program Chronology of the TPC Project: We are here!

ALICE-LHCC Review January 29-30, 2001 Thomas C. Meyer/EP-AIT24 Field Cage: Summary Performance –All technical issues have been studied, certifying the viability of the chosen field cage principle. Reliability –No serious risks have been identified, except..  charging at high particle flux (tests underway) Schedule is very tight due to increased in-house production load.